1. Field of the Invention
The present invention relates to an intake control apparatus configured and arranged to control the amount of intake air drawn into cylinders of an internal combustion engine. More particularly, the present invention relates to an intake control apparatus for internal combustion engine that accomplishes control of the intake air amount by combining variable control of a valve lift characteristic of the intake valve with a control of opening degree of a so-called electronically controlled throttle valve.
2. Background Information
The intake air amount of a gasoline engine is generally controlled by controlling a throttle opening degree of a throttle valve provided in an intake passage. As is well known, this method has the problem of a large pumping loss during low to medium load operations when the throttle opening degree of the throttle valve is small. Meanwhile, there have been attempts in the past to control the intake air amount independently of the throttle valve by changing the opening/closing timing and the lift amount of the intake valves. Thus, a “throttle-less” construction has been proposed which, similarly to a diesel engine, does not have a throttle valve in the air intake system and the control of the intake air amount is accomplished by controlling the valve lift characteristic.
Japanese Laid-Open Patent Publication No. 2002-89341 discloses a variable valve operating mechanism which accomplishes continuous variable control of the lift and duration of the intake valves. With a variable valve operating mechanism of the type described in this publication, the amount of intake air drawn into the cylinders can be varied independently of the throttle opening degree of the throttle valve, as mentioned above. Particularly when the engine is operating in small-load regions, throttle-less operation or operation in which the throttle valve opening degree is kept sufficiently large can be accomplished and the pumping loss can be greatly reduced.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved intake control apparatus for internal combustion engine. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.